1. Field of the Invention
The present invention relates, in general, to a method of decoding a Physical Broadcast Channel (PBCH) in a Long Term Evolution (LTE) system and, more particularly, to a scheme for detecting a Master Information Block (MIB) contained in a PBCH.
2. Description of the Related Art
A Master Information Block (MIB) in a Long Term Evolution (LTE) downlink contains the following four types of important information frequently used when a terminal that receives a downlink signal detects the signal.
1) Downlink bandwidth information
2) Physical Hybrid-automatic repeat request (ARQ) Indicator Channel (PHICH) duration information
3) PHICH resource information
4) System frame number
FIG. 1 is a diagram showing a process for transmitting a PBCH to an LTE downlink.
MIB information is configured in the form of a Physical Broadcast Channel (PBCH) in a physical layer using the process shown in FIG. 1 and is then transmitted a total of four times every 10 ms (frame length). That is, a single signal obtained by encoding MIB is divided and transmitted for a period of 40 ms. The four PBCHs transmitted every 10 ms for a period of 40 ms include the same MIB, but are transformed into different signals via scrambling and then transmitted.
When the terminal receives a PBCH signal, the terminal must find the following two types of information so as to decode the received PBCH and obtain an MIB.
1) Frame numbers in which a base station transmits the PBCH are required in a scrambling process.
2) Information about the number of transmit antennas of the base station is required so as to eliminate a PBCH Cyclic Redundancy Check (CRC) mask.
The terminal may obtain an MIB via decoding only after detecting both the above two types of information. However, since the above two types of information are contained in the received PBCH signal itself, a blind decoding method must be applied which performs all decoding operations in consideration of all possible cases and finds cases having no error in a CRC check. First, the total number of times that blind descrambling and decoding are processed to detect transmission frame numbers is four, which corresponds to frame transmission numbers. Further, the number of blind CRC checks for finding the number of transmit antennas is three, which corresponds to the number of transmit antennas per frame. Therefore, the blind PBCH decoding process actually requires a total of 12 operation processes, as shown in FIG. 2.